Comment by jwise0 | Hacker News Reader

Comment by jwise0 | Hacker News Reader

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Ha, yes, good point :-) I didn't write about that, but I did take some pictures of failed attempts at that.

That's one of the first things I did, actually. After dumping the contents of the flash off, I went on Amazon and hit 'reorder' on the same SD card that I'd bought before. Unfortunately, it was not the same: in the picture [1], the left is the one I'd purchased this time, and the right is the one I'd destroyed. The deals that low-cost SD card makers get on NAND flash vary greatly from day to day, so they just manufacture based on whatever controller and flash combination they can get cheapest on any given day: even the same SKU is unlikely to stay the same internally very long.

I did also try soldering to the BGA pads on the damaged one [2] [3], but no joy: I imagine that there were some traces that went backwards on the board before going towards the controller (for instance, to meet the TSOP leads), and on inserting the SD card into my laptop, I still had no signs of life.

[1] http://joshuawise.com/photos/etc/sd-card/sd-fux-11.xscale.jp...

[2] http://joshuawise.com/photos/etc/sd-card/sd-fux-13.xscale.jp...

[3] http://joshuawise.com/photos/etc/sd-card/sd-fux-15.xscale.jp...

5 minutes of googling == 6 months of reverse engineering :)

recovery tools for SM2683EN flash controller: http://www.usbdev.ru/files/smi/

xor formulas and block structure for Transcend card: http://flash-extractor.com/library/SM/EN2683/EN2683b%20BA__e...

Well, 5 minutes of googling and 6 months of learning russian :)

Aha, very good! Yes, I had seen the second link -- and, in fact, posted on the Soft-Center forums at the time. It gave me some of the basic information, but sadly, without the "key" to what some of that means, it's not terribly useful to me :-( for instance, I'm still not sure what "xor 0186" means, and how that translates to the whitening scheme I saw.

The "Update size" and "Update enable" did give me the idea to do what I called 'sector updates'. Do you have any more information on how those work?

I didn't have that 'usbdev.ru' site at the time. That page seems specific to the USB versions, not the SD card (SM2683) parts; unfortunately, I speak very little Russian. Do you have any particular parts I should ook at?

Thanks so much for any help you might be able to provide! I'd like to fill in the blanks in my knowledge of these things; in particular, I'd feel a lot more comfortable if I knew how the sector updates worked...

I'm always humbled when I see other peoples soldering skills. goddamn. And I love reading this type of stuff, doing things just "because". I found a rusty usb under a overpass a few months ago, after some cleaning/soldering/tricks I was finally able to read it and it turned out to be some kids schoolwork from 3 years ago haha

on a side I would suggest posting this over at hackaday, the marketers-pretending-to-be-hackers crowd here won't appreciate this.

Thanks. My soldering skills are not particularly special, though magnification certainly helps steady the hand! In the end, the real saviour here was the Schmartboard, which has these nicely recessed divots in the board that you can just 'push' solder along.

I'll consider sending this to Hackaday, too -- thanks for the reminder. That said, I've found that the HackerNews audience is pretty diverse in interest; you might be surprised what comes between the startup fever...

although the account is new I've been lurking for some time. [deleted tirade] in short, no I would not and am not surprised. this article was a nugget buried inside a mountain of irrelevant shit.

I loved the writeup! thanks for the detailed writeup and notes. Very impressive.

Very cool hack, I love reading stuff like this, thank you for sharing your experience and knowledge. I was going to ask the same question about just re-soldering onto a new SD Card of a similar type, I was wondering if the controllers can detect the exact chip type they are connected to, if so it might work. Also, for de-soldering and soldering SMT's the hot air re-work station makes it easy, never hurts to have the right tools :)

Unfortunately, it was not the same: in the picture [1], the left is the one I'd purchased this time, and the right is the one I'd destroyed.

The one you destroyed has a single Samsung 128Gbit TLC flash; the one you bought has a pair of Micron 64Gbit MLC. I'd say the latter is almost certainly better from a reliability perspective, and probably even cost more to manufacture.

Maybe, if they're buying the memory at market prices. I believe that for high-volume NAND flash consumers, there is probably more of a spot-pricing scheme in place: for whatever reason, if Micron had a whole bunch of 64Gbit MLC around because (say) HTC stopped making a phone yesterday, then Transcend would be plenty happy to scoop it up for a low price.

(edit: Googling for NAND flash spot pricing results in http://www.dramexchange.com , which seems to confirm those sorts of suspicions. I think the market is probably pretty volatile...)

SD cards are the lowest bin tier as well, given their low performance requirements and low margins relative to SSDs, embedded designs, etc. The leftovers and rejects tend to end up in that channel.

In that vein, the 64Gbit micron devices may in fact be 128Gbit die with half dead arrays -- so they may have a similar process node and reliability to the samsung device.

The MLC is undoubtedly superior to TLC however.

Ah I see, it would've been too easy then :). Thanks for the detailed response!

Brilliant work and excellent write-up. Thanks for sharing your efforts!

Just chiming in to second this.

Crazy to think what archaeologists may have to deal with in a 1000 years. Or (a little more sci-fi) findings at other planets.

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